Gabapentin vs. Cymbalta: What's the difference?

What is gabapentin? What is Cymbalta?

Gabapentin is an anti-seizure (anticonvulsant) drug used to prevent seizures and to treat post-herpetic neuralgia, the pain that follows an episode of shingles. Gabapentin structurally resembles the neurotransmitter gamma aminobutyric acid (GABA). It is believed that this similarity is related to gabapentin's mechanism of action. In animal models used for testing the anticonvulsant and analgesic (anti-pain) activities of drugs, gabapentin prevents seizures and reduces pain-related responses. Off-label uses for gabapentin include alcohol withdrawal, cocaine withdrawal, hiccups, restless leg syndrome, hyperhidrosis, headaches, diabetic neuropathy, hot flashes, and fibromyalgia.

Cymbalta (duloxetine) is a selective serotonin and norepinephrine reuptake inhibitor (SNRI) antidepressant used to treat depression, generalized anxiety disorder, pain associated with diabetic peripheral neuropathy, fibromyalgia, and chronic musculoskeletal pain. Other SNRIs include milnacipran (Savella), venlafaxine (Effexor), and desvenlafaxine (Pristiq). Cymbalta affects the neurotransmitters serotonin and norepinephrine, and many experts believe an imbalance among neurotransmitters is the cause of depression and other psychiatric disorders. Cymbalta works by preventing the reuptake of serotonin and epinephrine by nerves after they have been released. The reduced uptake increases the effect of serotonin and norepinephrine in the brain. The mechanism responsible for its effectiveness treating pain is not known but also is thought to involve its effects on serotonin and norepinephrine in the brain.

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What are the side effects of gabapentin and Cymbalta?

Gabapentin

The most common side effects of gabapentin are:

Other adverse effects and serious side effects associated with gabapentin include:

Antiepileptic medications have been associated with an increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidal thoughts, or unusual changes in behavior.

Cymbalta

The most common side effects of duloxetine are nausea, dry mouth, constipation, diarrhea, fatigue, difficulty sleeping, and dizziness. Increased blood pressure can occur and should be monitored. Seizures have been reported. Sexual dysfunction (decreased sex drive and delayed orgasm and ejaculation) has been associated with duloxetine.

Some patients may experience withdrawal reactions upon stopping duloxetine. Symptoms of withdrawal include:

  • dizziness,
  • anxiety,
  • nausea,
  • vomiting,
  • nervousness,
  • diarrhea,
  • irritability, and
  • insomnia.

The dose of duloxetine should be gradually reduced when therapy is discontinued to prevent symptoms of withdrawal.

Antidepressants increased the risk of suicidal thinking and behavior (suicidality) in short-term studies in children and adolescents with depression and other psychiatric disorders. Anyone considering the use of duloxetine or any other antidepressant in a child or adolescent must balance this risk with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidality, or unusual changes in behavior.

What is the dosage of gabapentin vs. Cymbalta?

Gabapentin

Gabapentin is available as:

  • Capsules: 100, 300, and 400 mg.
  • Tablets: 100, 300, 400, 600, and 800 mg.
  • Solution: 250 mg/5 ml
  • The recommended dose for postherpetic neuralgia is 1800 mg daily in 3 divided doses (Neurontin) or 1800 mg once daily (Gralise). Gralise is not interchangeable with other gabapentin products.
  • Seizures are treated with 900-1800 mg/daily in 3 divided doses (Neurontin). Withdrawal of treatment should occur slowly over a week.

Gabapentin may be taken with or without food.

Cymbalta

The recommended dose for treating depression is 20 or 30 mg twice daily or 60 mg once daily. Patients may be started with 30 mg once daily for one week before the dose is advanced to 60 mg daily.

The recommended dose for anxiety disorder, pain associated with diabetic neuropathy, fibromyalgia, or chronic musculoskeletal pain is 60 mg daily. Starting at 30 mg daily for one week before increasing to 60 mg daily may help patients adjust to the drug. There is no evidence that doses greater than 60 mg/day provide additional benefits. However, the maximum dose for depression or anxiety disorder is 120 mg/day.

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What drugs interact with gabapentin and Cymbalta?

Gabapentin

  • Antacids reduce the concentration of gabapentin in blood. Therefore, gabapentin should be administered 2 hours or more after taking antacids.
  • Morphine significantly increases blood concentrations of gabapentin and may increase central nervous system-related adverse events associated with gabapentin.

Cymbalta

  • Duloxetine should not be used in combination with a monoamine oxidase inhibitor (MAOI) such as phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), and selegiline (Eldepryl), or within 14 days of discontinuing the MAOI. At least 5 days should be allowed after stopping duloxetine before starting an MAOI. Combinations of SNRIs and MAOIs may lead to serious, sometimes fatal, reactions including very high body temperature, muscle rigidity, rapid fluctuations of heart rate and blood pressure, extreme agitation progressing to delirium, and coma. Similar reactions may occur if duloxetine is combined with antipsychotics, tricyclic antidepressants or other drugs that affect serotonin in the brain. Examples include tryptophan, sumatriptan (Imitrex), lithium, linezolid (Zyvox), tramadol (Ultram), and St. John’s Wort.
  • Fluoxetine (Prozac, Serafem), paroxetine (Paxil, Paxil CR, Pexeva), fluvoxamine (Luvox), and quinidine increase blood levels of duloxetine by reducing its metabolism in the liver. Such combinations may increase adverse effects of duloxetine.
  • Combining duloxetine with aspirin, nonsteroidal antiinflammatory drugs (NSAIDs), warfarin (Coumadin) or other drugs that are associated with bleeding may increase the risk of bleeding, because duloxetine itself is associated with bleeding.
  • Duloxetine has an enteric coating that prevents dissolution until it reaches a segment of the gastrointestinal that has a pH higher than 5.5. In theory, drugs that raise the pH in the gastrointestinal system (for example, Prilosec) may cause duloxetine to be released early while conditions that slow gastric empyting (for example, diabetes) may cause premature breakdown of duloxetine. Nevertheless, aAdministration of duloxetine with an antacid or famotidine (Axid) did not significantly affect the absorption of duloxetine.
  • Duloxetine may reduce the breakdown of desipramine (Norpramine), leading to increased blood concentrations of desipramine and potential side effects.

Are gabapentin and Cymbalta safe to take while pregnant or breastfeeding?

Gabapentin

  • Doctors do not know the safety of gabapentin during pregnancy.
  • Gabapentin is secreted in human breast milk; therefore, if you are pregnant you should only use this medication if the benefits outweigh the unknown risk to the fetus.

Cymbalta

  • Duloxetine is excreted into the milk of lactating women. Because the safety of duloxetine in infants is not known, breastfeeding while on duloxetine is not recommended.

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Summary

Gralise (gabapentin) and Cymbalta (duloxetine) are used to treat different types of neuralgia (nerve pain). Gabapentin is used postherpetic neuralgia from herpes zoster (nerve damage from shingles) and to treat seizure disorders. Cymbalta is used to treat pain associated with diabetic peripheral neuropathy, depression, generalized anxiety disorder, fibromyalgia, and chronic musculoskeletal pain.

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Medically Reviewed on 7/22/2019
References
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